About the mbuf timestamp (regardless of size etc.) accuracy: We should also consider the clock source. If the NIC HW is the clock source, there will be a fixed offset from the CPU's clock, but there will also be varying drift (they have separate XTALs). And if there are multiple NICs, there will be offset and varying drift between their clocks too.
If I remember correctly, the IEEE Ethernet specifications require a clock accuracy of 100 ppm. So XTALs of this quality are probably being used in the hardware. This means that the clock drift between two NICs (or a NIC and the actual time) can be in the magnitude of 100.000 ns per second. BTW: If you are interested in NTP, you should take a look at Poul-Henning Kamp's ntimed research: http://phk.freebsd.dk/time/index.html Med venlig hilsen / kind regards - Morten Br?rup
